Many homes employ a heating unit which operates by the combustion of supplied gas, and the distribution of the heat produced to the various rooms in the home by a network of forced air ducts and air return ducts. These central heating units can, under certain operating conditions exhaust undesirable levels of supplied gas and gas which is a byproduct of combustion, such as carbon monoxide, into the forced air ducts.
Further, many central heating units operate in conjunction with a central air conditioning unit. These units generally operate by pumping heat from the house to an outdoor heatsink by means of a closed compression/evaporation system operating on a refrigerant. If a leak occurs in this closed system, refrigerant can be exhausted into the forced air ducts.
Prior art devices, such as the device disclosed in U.S. Pat. No. 4,893,113 issued to Park et al. are capable of detecting the presence of carbon monoxide in the air surrounding a heating unit and activating an alarm.
Further, Japanese patent number 62-225829 discloses a control device for a heating unit which calculates the concentration of carbon monoxide in the room the heating unit is placed in and terminates combustion based upon this calculated concentration. These prior art devices do not disable the heating unit in response to the detection of undesired gases.